Bio-electrode and methods for manufacturing the bio-electrode

ABSTRACT

The present invention provides a bio-electrode that is excellent in conductivity and biocompatibility, is light-weight, can be manufactured at low cost, and can control significant reduction in conductivity even though the bio-electrode is soaked in water or dried. The present invention is accomplished by providing a conductive substrate and a living body contact layer formed on the conductive substrate, where the living body contact layer is a cured product of a bio-electrode composition including an (A) ionic material and a (B) resin other than the component (A), in which the component (A) has both a repeating unit “a” of a lithium salt, a sodium salt, a potassium salt, or an ammonium salt of sulfonamide including a partial structure represented by the following general formula (1) and a repeating unit “b” having a silicon atom, —R1—C(═O)—N−—SO2—Rf1M+(1).

This is a Divisional of application Ser. No. 15/882,406 filed Jan. 29,2018, which claims the benefit of Japanese Application No. 2017-24652filed Feb. 14, 2017. The disclosures of the prior applications arehereby incorporated by reference herein in their entireties.

TECHNICAL FIELD

The present invention relates to a bio-electrode that is used in contactwith the skin of a living body capable of detecting physical conditionssuch as heart rate by an electric signal transmitted from the skin, amethod for manufacturing the bio-electrode, a bio-electrode compositiondesirably used in the bio-electrode, and a polymer desirably used in thebio-electrode composition.

BACKGROUND

A recent growing popularity of Internet of Things (IoT) has acceleratedthe development of such major wearable devices as watches and glassesthat allow for Internet access. Even in the fields of medicine andsports, wearable devices for constantly monitoring the user's physicalstate are increasingly demanded, and such technological development isexpected to be further encouraged.

In the field of medicine, including an electrocardiogram for detectingan electric signal to measure the motion of the heart, use of wearabledevices for monitoring the state of human organs by detecting extremelyweak current has been examined. The electrocardiogram measurement isconducted by attaching an electrode coated with a conductive paste to abody, but this is a single (not continuous), short-time measurement. Onthe other hand, the above medical wearable device is aimed at monitoringthe state of physical conditions for a few weeks. Accordingly, abio-electrode used in a medical wearable device is required to make nochanges in conductivity even in long-time use and cause no skin allergy.In addition to these, bio-electrodes must be light-weight and producedat low cost.

Medical wearable devices are classified into two types: direct bodyattachment and clothing attachment. One typical body attachment deviceis a bio-electrode formed of a hydrophilic gel containing water andelectrolytes as ingredients of the above conductive paste (PatentDocument 1). The hydrophilic gel, containing sodium, potassium, andcalcium electrolytes in a hydrophilic polymer containing water, detectschanges in ion concentration from the skin to convert the data intoelectricity. Meanwhile, one typical clothing attachment device ischaracterized by a method for using as an electrode a fabric including aconductive polymer, such as PEDOT-PSS(Poly-3,4-ethylenedioxythiophene-polystyrenesulfonate), and a silverpaste incorporated into the fiber (Patent Document 2).

However, the use of the hydrophilic gel containing water andelectrolytes unfortunately brings about loss of conductivity due towater evaporation in drying process. Meanwhile, the use of a higherionization tendency metal such as copper can cause some users to sufferfrom skin allergy, as well as a conductive polymer such as PEDOT-PSS dueto strong acidity.

By taking advantage of excellent conductivity, the use of electrodematerials formed of metal nanowire, carbon black, or carbon nanotube hasbeen examined (Patent Documents 3, 4, and 5) With higher contactprobability, metal nanowires can conduct electricity in small quantitiesto be added. Nevertheless, metal nanowires, formed of a pointed thinmaterial, may cause skin allergy. Likewise, carbon nanotubes canstimulate a living body. Although the carbon black is not as poisonousas carbon nanotube, it also stimulates the skin. Accordingly, eventhough these electrode materials themselves cause no allergic reaction,the biocompatibility can be degraded depending on the shape of amaterial and its inherent stimulation, thereby failing to satisfy bothconductivity and biocompatibility.

Although metal films seem to function as an excellent bio-electrodethanks to extremely high conductivity, this is not always the case. Uponheartbeat, the human skin releases a sodium ion, a potassium ion, or acalcium ion, instead of extremely weak current. It is thus necessary toconvert changes in ion concentration into current, which is what lessionized precious metals unfortunately fail to do efficiently. Theresulting bio-electrode including the precious metal is characterized byhigh impedance and high resistance to the skin during electricalconduction.

Meanwhile, the use of a battery containing an ionic liquid has beenexamined (Patent Document 6). Advantageously, the ionic liquid isthermally and chemically stable, and the conductivity is excellent,providing more various battery applications. However, an ionic liquidhaving smaller molecular weight shown in Patent Document 6 unfortunatelydissolves into water. A bio-electrode containing such an ionic liquid inuse allows the ionic liquid to be extracted from the electrode bysweating, which not only lowers the conductivity, but also causes roughskin by the liquid soaking into the skin.

In addition, any bio-electrode fails to get biological information whenit is apart from the skin. The detection of even changes in contact areacan vary quantities of electricity traveling through the electrode,allowing the baseline of an electrocardiogram (electric signal) tofluctuate. Accordingly, in order to stably detect electric signals fromthe body, the bio-electrode is required to be in constant contact withthe skin and make no changes in contact area. This requirement issatisfied, preferably by use of adhesive bio-electrodes. Moreover,elastic and flexible bio-electrodes are needed to follow changes in skinexpansion and flexion.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: International Patent Laid-Open Publication No. WO2013/039151Patent Document 2: Japanese Unexamined Patent publication (Kokai) No.2015-100673Patent Document 3: Japanese Unexamined Patent publication (Kokai) No.H5-095924Patent Document 4: Japanese Unexamined Patent publication (Kokai) No.2003-225217Patent Document 5: Japanese Unexamined Patent publication (Kokai) No.2015-019806Patent Document 6: Japanese Unexamined Patent publication (Kokai) No.2004-527902

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The present invention was made in view of the situation to solve theproblems, and has an object to provide a bio-electrode compositioncapable of forming a living body contact layer for a bio-electrode thatis excellent in conductivity and biocompatibility, is light-weight, canbe manufactured at low cost, and can control significant reduction inconductivity even though the bio-electrode is soaked in water or dried,a bio-electrode including a living body contact layer formed of thebio-electrode composition, a method for manufacturing the bio-electrode,and a polymer desirably used in the bio-electrode composition.

Means for Solving the Problem

To solve these problems, the present invention provides a bio-electrodecomposition including an (A) ionic material and a (B) resin other thanthe component (A), wherein the component (A) has both a repeating unit“a” of a lithium salt, a sodium salt, a potassium salt, or an ammoniumsalt of sulfonamide having a partial structure represented by thefollowing general formula (1) and a repeating unit “b” having a siliconatom,

—R¹—C(═O)—N⁻—SO₂—Rf₁M⁺  (1)

wherein, R¹ represents a single bond, or a linear, a branched, or acyclic divalent hydrocarbon group having 1 to 40 carbon atoms, which maybe substituted by a heteroatom, or mediated by a heteroatom; Rf₁represents a linear or a branched alkyl group or a phenyl group having 1to 4 carbon atoms, having one or more fluorine atoms or atrifluoromethyl group; and M⁺ represents any of a lithium ion, a sodiumion, a potassium ion, or an ammonium ion.

The bio-electrode composition thus obtained can include a living bodycontact layer for a bio-electrode that is excellent in conductivity andbiocompatibility, is light-weight, can be produced at low cost, and cancontrol significant reduction in conductivity even though thebio-electrode is soaked in water or dried.

Also, the component (A) is preferably a polymer including repeatingunits “a1” and “b1” represented by the following general formula (2) asthe repeating units “a” and “b”, respectively,

wherein, R¹, Rf₁, and M⁺ represent the same meanings as before; each ofR² and R³ independently represents a hydrogen atom or a methyl group; X₁represents any of a single bond, a phenylene group, a naphthylene group,an ether group, an ester group, or an amide group; X₂ represents any ofan arylene group having 6 to 12 carbon atoms, a —C(═O)—O—R⁷— group, or a—C(═O)—NH—R⁷— group; R⁷ represents any of a single bond, a linear, abranched, or a cyclic alkylene group, or a phenylene group having 2 to12 carbon atoms, and may include one or more groups selected from anether group, a carbonyl group, an ester group, and an amide group; eachof R⁴, R⁵, and R⁶ independently represents a linear, a branched, or acyclic alkyl group having 1 to 6 carbon atoms, or an aryl group having 6to 10 carbon atoms, and may include one or more selected from a siloxanebond, a silicon atom, and a halogen atom; R⁴ and R⁵, or R⁴, R⁵, and R⁶may be bonded to form a ring or a three-dimensional structure; and “a1”and “b1” are numbers satisfying the equations 0<a1<1.0, 0<b1<1.0.

The bio-electrode composition including such a component (A) can form aliving body contact layer that is more excellent in conductivity andbiocompatibility. Copolymerization of a repeating unit “b1” containing asilicon atom can improve the water repellency, and a dry electrode filmincluding the polymer that is brought in contact with the skin is lessaffected by sweating or moisture.

In addition, the component (A) is preferably a polymer including arepeating unit “d” represented by the following general formula (2)′, inaddition to the repeating units “a” and “b”,

wherein, R⁸ represents a hydrogen atom or a methyl group; X₃ representsany of a single bond, a phenylene group, a naphthylene group, an ethergroup, an ester group, a phenylene group having an ester group, or anamide group; R⁹ represents a linear or a branched alkylene group having1 to 80 carbon atoms, having at least one ether group, and may includean aromatic group; and “d” is a number satisfying the equation 0≤1d<1.0.

The component (A) including such a repeating unit “d” having an etherchain, can form a bio-electrode film having improved ion conductivityand higher precision.

The component (A) preferably includes an ammonium ion represented by thefollowing general formula (3) as the M⁺,

wherein, each of R^(101d), R^(101e), R^(101f), and R^(101g)independently represents any of a hydrogen atom, a linear, a branched,or a cyclic alkyl group having 1 to 12 carbon atoms, a linear, abranched, or a cyclic alkenyl group or an alkynyl group having 2 to 12carbon atoms, or an aromatic group having 4 to 20 carbon atoms, and mayinclude one or more selected from an ether group, a carbonyl group, anester group, a hydroxy group, an amino group, a nitro group, a sulfonylgroup, a sulfinyl group, a halogen atom, and a sulfur atom; R^(101d) andR^(101e), or R^(101d), R^(101e), and R^(101f) may form a ring togetherwith a nitrogen atom bonded thereto, and in this case, R^(101d) andR^(101e), or R^(101d), R^(101e), and R^(101f) represent an alkylenegroup having 3 to 10 carbon atoms, or form a heteroaromatic ring havinga nitrogen atom in the formula in the ring.

The bio-electrode composition including such a component (A) can form aliving body contact layer that is more excellent in conductivity andbiocompatibility.

In addition, the component (B) preferably includes a silicone resinhaving a R_(x)SiO_((4-x)/2) unit, wherein R represents a substituted oran unsubstituted monovalent hydrocarbon group having 1 to 10 carbonatoms, and x represents a number of 2.5 to 3.5, and a SiO₂ unit,diorganosiloxane having an alkenyl group, and organohydrogenpolysiloxane having a SiH group.

The bio-electrode composition including such a component (B) can form aliving body contact layer that is particularly favorable incompatibility of the component (A) and the component (B), adhesion to aconductive substrate, adhesion to the skin, elasticity, and waterrepellency.

Preferably, the bio-electrode composition further includes an organicsolvent.

Such an organic solvent can further improve the application of abio-electrode composition.

Preferably, the bio-electrode composition further includes a carbonmaterial.

Such a bio-electrode composition can form a living body contact layerthat is more excellent in conductivity.

Preferably, the carbon material is formed of carbon black and/or carbonnanotube.

Such a carbon material can particularly desirably be used in thebio-electrode composition of the present invention.

The present invention provides a bio-electrode including a conductivesubstrate and a living body contact layer formed on the conductivesubstrate, wherein the living body contact layer is a cured product ofthe bio-electrode composition.

The bio-electrode thus obtained can form a living body contact layerthat is excellent in conductivity and biocompatibility, is light-weight,can be manufactured at low cost, and can control significant reductionin conductivity even though the bio-electrode is soaked in water ordried.

Preferably, the conductive substrate includes one or more substancesselected from gold, silver, silver chloride, platinum, aluminum,magnesium, tin, tungsten, iron, copper, nickel, stainless, chromium,titanium, and carbon.

Such a conductive substrate can particularly desirably be used in thebio-electrode of the present invention.

The present invention provides a method for manufacturing abio-electrode including a conductive substrate and a living body contactlayer formed on the conductive substrate, including: applying thebio-electrode composition to the conductive substrate to be cured toform the living body contact layer.

The manufacturing method thus obtained can readily manufacture at lowcost a bio-electrode including a living body contact layer that isexcellent in conductivity and biocompatibility, is light-weight, andcontrols significant reduction in conductivity even though thebio-electrode is soaked in water or dried.

Preferably, the conductive substrate includes one or more substancesselected from gold, silver, silver chloride, platinum, aluminum,magnesium, tin, tungsten, iron, copper, nickel, stainless, chromium,titanium, and carbon.

Such a conductive substrate can particularly desirably be used in themethod for manufacturing a bio-electrode of the present invention.

The present invention provides a polymer including repeating units “a1”and “b1” represented by the following general formula (2),

wherein, R¹ represents a single bond, or a linear, a branched, or acyclic divalent hydrocarbon group having 1 to 40 carbon atoms, which maybe substituted by a heteroatom, or mediated by a heteroatom; Rf₁represents a linear or a branched alkyl group or a phenyl group having 1to 4 carbon atoms, having one or more fluorine atoms or atrifluoromethyl group; M⁺ represents any of a lithium ion, a sodium ion,a potassium ion, or an ammonium ion; each of R² and R³ independentlyrepresents a hydrogen atom or a methyl group; X₁ represents any of asingle bond, a phenylene group, a naphthylene group, an ether group, anester group, or an amide group; X₂ represents any of an arylene grouphaving 6 to 12 carbon atoms, a —C(═O)—O—R⁷— group, or a —C(═O)—NH—R⁷—group; R⁷ represents any of a single bond, a linear, a branched, or acyclic alkylene group, or a phenylene group having 2 to 12 carbon atoms,and may include one or more groups selected from an ether group, acarbonyl group, an ester group, and an amide group; each of R⁴, R⁵, andR⁶ independently represents a linear, a branched, or a cyclic alkylgroup having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbonatoms, and may include one or more selected from a siloxane bond, asilicon atom, and a halogen atom; R⁴ and R⁵, or R⁴, R⁵, and R⁶ may bebonded to form a ring or a three-dimensional structure; “a1” and “b1”are numbers satisfying the equations 0<a1<1.0, 0<b1<1.0.

Such a polymer can desirably be used in a bio-electrode compositioncapable of forming a living body contact layer for a bio-electrode thatis excellent in conductivity and biocompatibility, is light-weight, canbe manufactured at low cost, and can control significant reduction inconductivity even though the bio-electrode is soaked in water or dried.

Preferably, the polymer includes, in addition to the repeating units“a1” and “b1” a repeating unit “d” represented by the following generalformula (2)′,

wherein, R⁸ represents a hydrogen atom or a methyl group; X₃ representsany of a single bond, a phenylene group, a naphthylene group, an ethergroup, an ester group, a phenylene group having an ester group, or anamide group; R⁹ represents a linear or a branched alkylene group having1 to 80 carbon atoms, having at least one ether group, and may includean aromatic group; d is a number satisfying the equation 0≤d<1.0.

The component (A) including such a repeating unit “d” having an etherchain, can form a bio-electrode film with improved ion conductivity andhigher precision.

Effect of the Invention

As described above, the bio-electrode composition of the presentinvention can form a living body contact layer for a bio-electrode thatis capable of efficiently transmitting electric signals from the skin toa device (or that is excellent in conductivity), generating no allergydespite its long-time attachment to the skin (or that is excellent inbiocompatibility), is light-weight, can be manufactured at low cost, andcan control significant reduction in conductivity even though thebio-electrode is soaked in water or dried. Also, the addition of acarbon material can further improve the conductivity, and a combined useof adhesive and elastic polymers can manufacture particularly adhesiveand elastic bio-electrodes. Furthermore, the use of additives canimprove the elasticity and adhesion to the skin. The resin constituentand the thickness of a living body contact layer can be adjusted asrequired to control the elasticity and adhesion. Accordingly, abio-electrode including a living body contact layer using such abio-electrode composition of the present invention is particularlydesirable as a bio-electrode used in medical wearable devices. Themethod for manufacturing a bio-electrode of the present invention canreadily manufacture such a bio-electrode at low cost. In addition, thepolymer of the present invention can desirably be used in thebio-electrode composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing one example of abio-electrode of the present invention;

FIG. 2 is a schematic cross-sectional view showing one example of abio-electrode of the present invention that is attached to a livingbody;

FIG. 3(a) is a schematic illustration of a bio-electrode manufacturedwith an Example of the present invention viewed from the living bodycontact layer side, and FIG. 3 (b) is a schematic illustration of thebio-electrode manufactured with an Example of the present inventionviewed from the conductive substrate side; and

FIG. 4 is an illustration showing that the impedance is measured on theskin surface, using a bio-electrode manufactured with an Example of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As described above, the development of a bio-electrode compositioncapable of forming a living body contact layer for a bio-electrode thatis excellent in conductivity and biocompatibility, is light-weight, canbe manufactured at low cost, and can control significant reduction inconductivity even though the bio-electrode is soaked in water or dried,a bio-electrode including a living body contact layer formed of thebio-electrode composition, a method for manufacturing the bio-electrode,and a polymer desirably used in the bio-electrode composition, isdemanded.

Inventors of the present invention have focused on an ionic liquid as anionic material (conductive material) to be blended into a bio-electrodecomposition for forming a living body contact layer for a bio-electrode.Advantageously, the ionic liquid is thermally and chemically stable, andthe conductivity is excellent, providing more various batteryapplications. Illustrative example of the ionic liquid includeshydrochloride, oxalate, iodate, trifluoromethane sulfonate,nonafluorobutanesulfonate salt, bis(trifluoromethane sulfonyl) imideacid salt, hexafluorophosphate salt, and tetrafluoroborate salt ofsulfonium, phosphonium, ammonium, morpholinium, pyridinium,pyrrolidinium, and imidazolium. However, since these salts (those havingsmaller molecular weight, in particular) are normally highlyhydrophilic, a bio-electrode for forming a living body contact layerfrom a bio-electrode composition including these salts is unfortunatelysubjected to salt extraction by sweating or washing to lower theconductivity. Since tetrafluoroborate salts are highly poisonous andother salts are highly water-soluble, they are readily immersed into theskin to cause rough skin (or, strong stimulation to the skin).

When an acid for forming a neutralization salt has a high acidity, theion polarization is significant to improve the ion conductivity, therebyallowing a lithium salt of bis (trifluoromethane sulfonyl) imide acid ortris (trifluoromethane sulfonyl) methide acid as a lithium-ion batteryto show high ion conductivity. Meanwhile, higher acid strength providesthe salt with stronger living body stimulation, showing a trade-offbetween ion conductivity and living body stimulation. Nevertheless,salts for bio-electrode applications must satisfy both high ionconductivity and low living body stimulation.

Inventors of the present invention have carried out an extendedinvestigation and found that a lithium salt, a sodium salt, a potassiumsalt, or an ammonium salt of sulfonamide in which a fluorosulfonic groupis bonded to one side of a nitrogen atom and a carbonyl group is bondedto the other side shows a lower acidity than a lithium salt, a sodiumsalt, a potassium salt, or an ammonium salt of bissulfonamide in which afluoroalkyl group is bonded to both sides of the sulfonamide, therebycausing lower living body stimulation, and high ion conductivity due tohigher acidity than a lithium salt, a sodium salt, a potassium salt, oran ammonium salt of sulfonamide in which a fluorosulfonic group isbonded to one side of a nitrogen atom and an alkyl group is bonded tothe other side. Also, higher molecular weight of an ion compound lowersthe immersion into the skin and the resulting stimulation to the skin,and the ion compound is preferably a polymer of high molecular weight.Inventors of the present invention conceived synthesis of a polymer bycopolymerizing a monomer containing a silicon atom using the ioncompound having a polymerizable double bond. Furthermore, inventors ofthe present invention found that by mixing the salt with e.g., asilicone-based, an acrylic-based, or a urethane-based adhesive agent(resin), a living body contact layer can be formed to satisfy bothconductivity and biocompatibility, control significant reduction inconductivity even though the bio-electrode is soaked in water or dried,and stably detect electric signals from a bio-electrode that is alwaysclose to the skin. Based on that information, the present invention wasaccomplished.

Specifically, the present invention provides a bio-electrode compositionincluding an (A) ionic material and a (B) resin other than the component(A), wherein the component (A) has both a repeating unit “a” of alithium salt, a sodium salt, a potassium salt, or an ammonium salt ofsulfonimide having a partial structure represented by the followinggeneral formula (1) and a repeating unit “b” having a silicon atom,

—R¹—C(═O)—N⁻—SO₂—Rf₁M⁺  (1)

wherein, R¹ represents a single bond, or a linear, a branched, or acyclic divalent hydrocarbon group having 1 to 40 carbon atoms, which maybe substituted by a heteroatom, or mediated by a heteroatom; Rf₁represents a linear or a branched alkyl group or a phenyl group having 1to 4 carbon atoms, having one or more fluorine atoms or atrifluoromethyl group; M⁺ represents any of a lithium ion, a sodium ion,a potassium ion, or an ammonium ion.

The present invention also provides a polymer including repeating units“a1” and “b1” represented by the following general formula (2),

wherein, R¹ represents a single bond, or a linear, a branched, or acyclic divalent hydrocarbon group having 1 to 40 carbon atoms, which maybe substituted by a heteroatom, or mediated by a heteroatom; Rf₁represents a linear or a branched alkyl group or a phenyl group having 1to 4 carbon atoms, having one or more fluorine atoms or atrifluoromethyl group; M⁺ represents any of a lithium ion, a sodium ion,a potassium ion, or an ammonium ion; each of R² and R³ independentlyrepresents a hydrogen atom or a methyl group; X₁ represents any of asingle bond, a phenylene group, a naphthylene group, an ether group, anester group, or an amide group; X₂ represents any of an arylene grouphaving 6 to 12 carbon atoms, a —C(═O)—O—R⁷— group, or a —C(═O)—NH—R⁷—group; R⁷ represents any of a single bond, a linear, a branched, or acyclic alkylene group, or a phenylene group having 2 to 12 carbon atoms,and may include one or more groups selected from an ether group, acarbonyl group, an ester group, and an amide group; each of R⁴, R⁵, andR⁶ independently represents a linear, a branched, or a cyclic alkylgroup having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbonatoms, and may include one or more selected from a siloxane bond, asilicon atom, and a halogen atom; R⁴ and R⁵, or R⁴, R⁵, and R⁶ may bebonded to form a ring or a three-dimensional structure; and “a1” and“b1” are numbers satisfying the equations 0<a1<1.0 and 0<b1<1.0.

The present invention will be described in detail, but the presentinvention is not restricted thereto.

Bio-Electrode Composition

The bio-electrode composition of the present invention includes an (A)ionic material and a (B) resin. Each component of the bio-electrode ofthe present invention will be described in more detail.

(A) Ionic Material (Salt)

The salt blended into the bio-electrode composition of the presentinvention as an (A) ionic material (conductive material) is a polymerincluding both a repeating unit “a” of a lithium salt, a sodium salt, apotassium salt, or an ammonium salt of sulfonamide having a partialstructure represented by the following general formula (1) with afluorosulfonic group bonded on one side of a nitrogen atom and acarbonyl group bonded on the other side, and a repeating unit “b” havinga silicon atom,

—R¹—C(═O)—N⁻—SO₂—Rf₁M⁺  (1)

wherein, R¹ represents a single bond, or a linear, a branched, or acyclic divalent hydrocarbon group having 1 to 40 carbon atoms, which maybe substituted by a heteroatom, or mediated by a heteroatom; Rf₁represents a linear or a branched alkyl group or a phenyl group having 1to 4 carbon atoms, having one or more fluorine atoms or atrifluoromethyl group; M⁺ represents any of a lithium ion, a sodium ion,a potassium ion, or an ammonium ion.

Preferably, a polymer salt blended into the bio-electrode composition ofthe present invention as an (A) ionic material is a polymer of thepresent invention including repeating units “a1” and “b1” represented bythe following general formula (2) as the above repeating units “a” and“b”,

wherein, R¹, Rf₁, and M represent the same meanings as before. Each ofR² and R³ independently represents a hydrogen atom or a methyl group; X₁represents any of a single bond, a phenylene group, a naphthylene group,an ether group, an ester group, or an amide group; X₂ represents any ofan arylene group having 6 to 12 carbon atoms, a —C(═O)—O—R⁷— group, or a—C(═O)—NH—R⁷— group; R⁷ represents any of a single bond, a linear, abranched, or a cyclic alkylene group, or a phenylene group having 2 to12 carbon atoms, and may include one or more groups selected from anether group, a carbonyl group, an ester group, and an amide group; eachof R⁴, R⁵, and R⁶ independently represents a linear, a branched, or acyclic alkyl group having 1 to 6 carbon atoms, or an aryl group having 6to 10 carbon atoms, and may include one or more selected from a siloxanebond, a silicon atom, and a halogen atom; R⁴ and R⁵, or R⁴, R⁵, and R⁶may be bonded to form a ring or a three-dimensional structure; and “a1”and “b1” are numbers satisfying the equations 0<a1<1.0 and 0<b1<1.0.

Repeating Unit “a”

The component (A) has a repeating unit “a” of a lithium salt, a sodiumsalt, a potassium salt, or an ammonium salt of sulfonimide having apartial structure represented by the general formula (1) of thebio-electrode composition of the present invention. The repeating unit“a” is preferably a repeating unit “a1” in the general formula (2).

The monomer of sulfonamide for obtaining the repeating unit “a1” in thegeneral formula (2) is represented by the following general formula (4),

wherein, R¹, R², X₁, Rf₁, and M⁺ represent the same meanings as before.

Illustrative example of the monomer represented by the general formula(4) includes the following monomers,

wherein, R² and M⁺ represent the same meanings as before.

Illustrative example of the method for synthesizing a monomer of alithium salt, an sodium salt, a potassium salt, or an ammonium salt forobtaining the repeating unit represented by the general formula (4)includes the method for reacting an oxychloride having a polymerizablegroup and fluoroalkane sulfonamide in the presence of a base in anorganic solvent represented by the following formula. The method forsynthesizing a monomer of the present invention is not restrictedthereto,

wherein, R¹, R², X₁, Rf₁, and M⁺ represent the same meanings as before.M^(a) represents a base.

In the above formula, the amount of oxychloride to be used is preferably0.5 to 3 moles, and more preferably 0.8 to 1.5 moles relative to 1 moleof fluoroalkane sulfonamide. Also, oxychloride can be synthesized by aknown method by action of oxalyl chloride and thionyl chloride oncarboxylic acid in an organic solvent from a corresponding carboxylicacid.

The fluoroalkane sulfonamide may be a commercially available product,and ammonia may be reacted with a corresponding fluoroalkanesulfonylhalides or fluoroalkane sulfonic acid anhydride for monomersynthesis.

The base M^(a) is not particularly restricted. Illustrative examplethereof includes lithium carbonate, lithium hydroxide, sodium carbonate,sodium hydroxide, sodium hydride, potassium carbonate, potassiumhydroxide, potassium hydride, trimethylamine, triethylamine,diisopropylethylamine, pyridine, lutidine, collidine, andN,N-dimethylaminopyridine. The amount of a base to be used is preferably1.0 to 4.0 moles relative to 1 mole of fluoroalkane sulfonamide. Formonomer synthesis, when M⁺ is a sodium ion, the sodium-based base can beused, and when M⁺ is a potassium ion, the potassium-based base can beused. When M⁺ is a tertiary or a quaternary ammonium ion, itscorresponding tertiary amine or quaternary amine salt can be used formonomer synthesis. When M⁺ is an ammonium ion, cation exchange issubjected to a monomer of a sodium ion or a potassium ion for monomersynthesis.

Illustrative example of the reaction solvent includes acetonitrile,chloride methylene, dichloroethane, acetone, 2-butanone, ethyl acetate,dimethyl formamide, N-methylpyrrolidone, tetrahydrofuran, 1,4-dioxane,toluene, xylene, hexane, heptane, and chlorobenzene can be usedsingularly or mixed in combination therewith, and can be reacted insolventless state. The reaction temperature is preferably −10° C. to aboiling point of a solvent, more preferably 0° C. to a boiling point ofa solvent. The reaction time is usually 30 minutes to 40 hours.

In the above formula, in place of oxychloride, acid anhydride can beused for a similar reaction, as well as a corresponding sulfonamide saltsuch as trifluoromethane sulfonamide potassium salt, in place offluoroalkane sulfonamide.

The component (A), as M⁺ in a repeating unit “a” (repeating unit “a1”),includes an ammonium ion (ammonium cation) represented by the followinggeneral formula (3),

wherein, each of R^(101d), R^(101e), R^(101f), and R^(101g)independently represents any of a hydrogen atom, a linear, a branched,or a cyclic alkyl group having 1 to 12 carbon atoms, a linear, abranched, or a cyclic alkenyl group or an alkynyl group having 2 to 12carbon atoms, or an aromatic group having 4 to 20 carbon atoms, and mayinclude one or more selected from an ether group, a carbonyl group, anester group, a hydroxy group, an amino group, a nitro group, a sulfonylgroup, a sulfinyl group, a halogen atom, and a sulfur atom; R^(101d) andR^(101e), or R^(101d), R^(101e), and R^(101f) may form a ring togetherwith a nitrogen atom bonded to these, and in this case, R^(101d) andR^(101e), or R^(101d), R^(101e), and R^(101f) represent an alkylenegroup having 3 to 10 carbon atoms, or form a heteroaromatic ring havinga nitrogen atom in the formula in the ring.

Illustrative example of the ammonium ion represented by the generalformula (3) includes the following ammonia,

Particularly preferably, the ammonium ion represented by the generalformula (3) is a tertiary or a quaternary ammonium ion.

Repeating Unit “b”

The component (A) of the bio-electrode composition of the presentinvention includes, in addition to the above repeating unit “a”, arepeating unit “b” having a silicon atom. The repeating unit “b” ispreferably a repeating unit “b1” in the general formula (2)

The monomer for obtaining the repeating unit “b1” in the general formula(2) is represented by the following general formula (5),

wherein, R³ to R⁶, and X₂ represent the same meanings as before.

Illustrative example of the monomer represented by the general formula(5) includes the following monomers,

wherein, “n” is an integer of 0 to 100.

Repeating Unit “c”

The component (A) of the bio-electrode composition of the presentinvention can be copolymerized with a monomer having two polymerizabledouble bonds in one molecule (repeating unit “c”), in addition to therepeating units “a” and “b”. The use of such a repeating unit “c” canimprove the crosslinking property of the component (A).

Illustrative example of the monomer for obtaining a repeating unit “c”includes the following monomers,

wherein, “n” is an integer of 0 to 100.

Repeating Unit “d”

The component (A) of the bio-electrode composition of the presentinvention can be copolymerized with a monomer having an oxymethylenestructure, an oxyethylene structure (glyme chain), or an oxypropylenestructure (repeating unit “d”), in addition to the repeating units “a”and “b”. The use of such a repeating unit “d” can improve theconductivity of the component (A).

Illustrative example of the monomer for obtaining a repeating unit “d”includes the one represented by the following general formula (2)″,

wherein, R⁸ represents a hydrogen atom or a methyl group; X₃ representsany of a single bond, a phenylene group, a naphthylene group, ethergroup, an ester group, a phenylene group having an ester group, or anamide group, R⁹ represents a linear, or a branched alkylene group having1 to 80 carbon atoms, having at least one ether group, and may includean aromatic group.

Illustrative example of the monomer for obtaining a repeating unit “d”includes the following monomers,

Repeating Unit “e”

The component (A) of the bio-electrode composition of the presentinvention can be copolymerized with a monomer containing a glyme chainhaving two polymerizable double bonds in one molecule (repeating unit“e”), in addition to the repeating units “a”, “b”, “c”, and “d”. The useof such a repeating unit “e” can improve the crosslinking property andion conductivity of the component (A).

Illustrative example of the monomer for obtaining a repeating unit “e”includes the following monomers,

One typical method for synthesizing a polymer of the component (A) maybe a method for obtaining a copolymer by adding an initiator of radicalpolymerization and subjecting a desired monomer out of monomers forproviding repeating units “a”, “b”, “c”, “d”, and “e” to heatpolymerization in an organic solvent.

Illustrative example of the organic solvent used in polymerizationincludes toluene, benzene, tetrahydrofuran, diethyl ether, and dioxane.Illustrative example of the polymerization initiator includes2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The heatingtemperature is preferably 50 to 80° C., and the reaction time ispreferably 2 to 100 hours, and more preferably 5 to 20 hours.

Herein, each of the repeating units “a”, “b”, “c”, “d”, and “e”independently satisfies the equations in ratio; 0<a<1.0, 0<b<1.0,0≤c<1.0, 0≤d<1.0, and 0≤e<1.0, preferably 0.1≤a≤0.9, 0.1≤b≤0.9, 0≤c≤0.6,0≤d≤0.6, and 0≤e≤0.6, and more preferably 0.2≤a≤0.8, 0.2≤b≤0.8, 0≤c≤0.5,0≤d≤0.5, and 0≤e≤0.5. Also, they satisfy the equation 0<a+b+c+d+e≤1. Theratios of the repeating units “a” and “b” may be equivalent to those ofthe repeating units “a1” and “b1”.

For example, “a+b+c+d+e=l” means that in a polymer including repeatingunits “a”, “b”, “c”, “d”, and “e”, the total amount of the repeatingunits “a”, “b”, “c”, “d”, and “e” is 100 mole % relative to the totalamount of all the repeating units, and “a+b+c+d+e<l” means that thetotal amount of the repeating units “a”, “b”, “c”, “d”, and “e” is under100 mole % relative to all the repeating units, showing the use of otherrepeating units other than the units “a”, “b”, “c”, “d”, and “e”.

The molecular weight of the component (A) is preferably 500 or more asweight average molecular weight, more preferably 1,000 or more and1,000,000 or less, and much more preferably 2,000 or more and 500,000 orless. When the amount of ionic monomer that is not incorporated into acomponent (A) after polymerization (residual monomer) is small, theresulting skin immersion is small enough to control skin allergy in abiocompatibility test. Preferably, the residual monomer is reduced to 10parts by mass or less relative to 100 parts by mass of the component(A).

The amount of the component (A) to be blended into the bio-electrodecomposition of the present invention is preferably 0.1 to 300 parts bymass, and more preferably 1 to 200 parts by mass relative to 100 partsby mass of the component (B). The component (A) may be used singularlyor mixed in combination with two or more components.

(B) Resin

The (B) resin blended into the bio-electrode composition of the presentinvention is a component for preventing salt elution by compatibilitywith the (A) ionic material (salt) and providing a conductive improversuch as carbon to express the adhesion. The resin may be a resin otherthan the component (A), preferably a thermosetting resin and/or aphotocurable resin, particularly one or more resins selected fromsilicone-based, acrylic-based, and urethane-based resins.

The adhesive silicone-based resin is an addition reaction curable resinor a radical crosslinking reaction curable resin. Illustrative exampleof the addition reaction curable resin includes diorganosiloxane havingan alkenyl group disclosed in Japanese Unexamined Patent publication(Kokai) No. 2015-193803, an MQ resin having R₃SiO_(0.5) and SiO₂ units,organohydrogen polysiloxane having a plurality of SiH groups, and aresin containing a platinum catalyst, an addition inhibitor, and anorganic solvent. Illustrative example of the radical crosslinkingreaction curable resin includes e.g., as disclosed in JapaneseUnexamined Patent publication (Kokai) No. 2015-193803,diorganopolysiloxane having an alkenyl group or not, an MQ resin havingR₃SiO_(0.5) and SiO₂ units, and a resin containing organic peroxide andan organic solvent. Herein, R represents a hydrocarbon group of asubstituted or an unsubstituted monovalent having 1 to 10 carbon atoms.

A compound including a combination of polysiloxane and a resin formed bycondensation reaction of polysiloxane having silanol at a polymerterminal or on a side chain and an MQ resin can be used. An MQ resin,containing silanol in large quantities, can be added to improve theadhesive strength, and its non-crosslinking structure leads to nointermolecular bonding with polysiloxane. As described above,integration of polysiloxane and a resin can enhance the adhesivestrength.

Also, modified siloxane having a group selected from an amino group, anoxirane group, an oxetane group, a polyether group, a hydroxy group, acarboxyl group, a mercapto group, a methacryl group, an acrylic group, aphenol group, a silanol group, a carboxylic acid anhydride group, anaryl group, an aralkyl group, an amide group, an ester group, and alactone ring can be added to the silicone-based resin. The addition ofmodified siloxane improves the dispersion in a silicone resin of thecomponent (A). In any modified siloxane, either or both terminals, or aside chain of siloxane may be modified.

The adhesive acrylic-based resin may include hydrophilic ester(meth)acrylate disclosed in Japanese Unexamined Patent publication(Kokai) No. 2016-011338, and long-chain hydrophobic ester (meth)acrylateas a repeating unit. In some cases, ester (meth)acrylate having afunctional group or ester (meth)acrylate having a siloxane bond may becopolymerized.

The adhesive urethane-based resin may have e.g., a urethane bonddisclosed in Japanese Unexamined Patent publication (Kokai) No.2016-065238, a polyether bond, a polyester bond, a polycarbonate bond,or a siloxane bond.

To prevent declines in conductivity due to elution of the component (A)from a living body contact layer, in the bio-electrode composition ofthe present invention, a (B) resin preferably has higher compatibilitywith the component (A). To prevent peeling of a living body contactlayer from a conductive substrate, in the bio-electrode composition ofthe present invention, a (B) resin preferably has high adhesion to aconductive substrate. To provide the resin with a higher compatibilitywith a conductive substrate and a salt, the use of highly polar resin iseffective. Illustrative example of the resin includes a resin containingone or more selected from an ether bond, an ester bond, an amide bond,an imide bond, a urethane bond, thiourethane bond, and a thiol group, apolyacrylic resin, a polyamide resin, a polyimide resin, a polyurethaneresin, and a polythiourethane resin. On the other hand, a living bodycontact layer is in contact with a living body to be readily affected bysweating from the living body. Accordingly, in the bio-electrodecomposition of the present invention, the (B) resin preferably has highwater repellency and less hydrolysis. To provide the resin with highwater repellency and less hydrolysis, use of a resin containing asilicon atom is effective.

The polyacrylic resin containing a silicon atom may desirably be apolymer having silicone on a main chain and a polymer having a siliconatom on a side chain. The polymer having silicone on a main chain may besiloxane having a (meth)acrylicpropyl group or silsesquioxane. In thiscase, a photo radical generator can be added to polymerize a(meth)acrylic portion to be cured.

The polyamide resins containing a silicon atom may desirably bepolyamide silicone resins in e.g., Japanese Unexamined Patentpublication (Kokai) No. 2011-079946 and U.S. Pat. No. 5,981,680. Thesepolyamide silicone resins can be synthesized by combining a siliconecompound having an amino group at both terminals and a non-siliconecompound having an amino group at both terminals, and a non-siliconecompound having a carboxyl group at both terminals and a siliconecompound having a carboxyl group at both terminals.

Also, polyamic acid before cyclization obtained by reaction ofcarboxylic acid anhydride and amine may be used. A carboxyl group ofpolyamic acid may be crosslinked, using an epoxy-based or anoxetane-based crosslinking agent, and a (meth) acrylate portion may besubjected to photo radical crosslinking by esterification reaction of acarboxyl group and hydroxyethyl(meth)acrylate.

The polyimide resin containing a silicon atom may desirably be e.g., apolyimide silicone resin disclosed in Japanese Unexamined Patentpublication (Kokai) No. 2002-332305. The polyimide resin issignificantly viscous, but a (meth) acrylic-based monomer can be blendedas a solvent and a crosslinking agent to reduce the viscosity of theresin.

The polyurethane resin containing a silicon atom may be a polyurethanesilicone resin. Such a polyurethane silicone resin can be crosslinked bya urethane bond by blending and heating a compound having an isocyanategroup at both terminals and a compound having a hydroxy group at oneterminal. In this case, however, a compound having an isocyanate groupat both terminals and/or a compound having a hydroxy group at oneterminal must contain a silicon atom (siloxane bond). As disclosed inJapanese Unexamined Patent publication (Kokai) No. 2005-320418, aurethane (meth) acrylate monomer can be blended into polysiloxane forphoto crosslinking. In addition, a polymer both having a siloxane bondand a urethane bond and having a (meth) acrylate group at one terminalcan be photo-crosslinked.

The polythiourethane resin containing a silicon atom can be obtained byreaction of a compound having a thiol group and a compound having anisocyanate group, and either of the compounds may contain a siliconatom. So long as one terminal includes a (meth) acrylate group, theresin can be photo cured.

In addition to diorganosiloxane having the alkenyl group, an MQ resinhaving R₃SiO_(0.5) and SiO₂ units, and organohydrogen polysiloxanehaving a plurality of SiH groups, modified siloxane having a groupselected from an amino group, an oxirane group, an oxetane group, apolyether group, a hydroxy group, a carboxyl group, a mercapto group, amethacryl group, an acrylic group, a phenol group, a silanol group, acarboxylic acid an anhydride group, an aryl group, an aralkyl group, anamide group, an ester group, and a lactone ring is added to thesilicone-based resin to enhance the compatibility with the salt.

As later described, a living body contact layer is a cured product of abio-electrode composition. The curing process can achieve favorableadhesion of a living body contact layer both to the skin and aconductive substrate. The curing step is not particularly restricted,and may be a commonly known one, e.g., by heating and/or light exposure,or by crosslinking reaction using an acid or a base catalyst. Thecrosslinking reaction may be selected according to Crosslinking ReactionHandbook, Yasuharu Nakayama, MARUZEN-YUSHODO Company, Limited. (2013)Chap. 2, pp. 51 to 371.

Diorganosiloxane having an alkenyl group and organohydrogen polysiloxanehaving a plurality of SiH groups can be crosslinked by addition reactionusing a platinum catalyst.

Illustrative example of the platinum catalyst includes chloroplatinicacid, an alcohol solution of chloroplatinic acid, a reactant ofchloroplatinic acid and alcohol, a reactant of chloroplatinic acid and aolefin compound, a reactant of chloroplatinic acid and siloxanecontaining a vinyl group, a platinum-based catalyst such as aplatinum-olefin complex and a siloxane complex containing aplatinum-vinyl group, and a platinum group metal-based catalyst such asa rhodium complex and a ruthenium complex. These catalysts may bedissolved or dispersed into an alcohol-based, a hydrocarbon-based, or asiloxane-based solvent.

The amount of the platinum catalyst to be added is preferably 5 to 2,000ppm, and particularly 10 to 500 ppm relative to 100 parts by mass of aresin.

When an addition curable silicone resin is used, an addition inhibitormay be added. The addition inhibitor is added as a quencher forgenerating no action of platinum catalyst in a solution and inlow-temperature environment before heat curing after forming a coatedfilm. Illustrative example thereof includes 3-methyl-1-butyne-3-ol,3-methyl-1-pentyne-3-ol, 3,5-dimethyl-1-hexyne-3-ol, 1-ethynylcyclohexanol, 3-methyl-3-trimethylsiloxy-1-butyne,3-methyl-3-trimethylsiloxy-1-pentyne,3,5-dimethyl-3-trimethylsiloxy-1-hexyne, 1-ethynyl-1-trimethylsiloxycyclohexane, bis(2,2-dimethyl-3-butynoxy)dimethylsilane,1,3,5,7-tetramethyl-1,3,5,7-tetravinyl cyclotetrasiloxane, and1,1,3,3-tetramethyl-1,3-divinyldisiloxane.

The amount of the addition inhibitor to be added is preferably 0 to 10parts by mass, and particularly 0.05 to 3 parts by mass relative to 100parts by mass of a resin.

Illustrative example of the photo curing method includes a method forusing a resin having a (meth)acrylate terminal or an olefin terminal,adding a crosslinking agent whose terminal is (meth) acrylate, olefin,or a thiol group, and adding a photo radical generator, and a method foradding a photo acid generator by using a resin having an oxirane group,an oxetane group, and a vinylether group or a crosslinking agent.

Illustrative example of the photo radical generator includesacetophenone, 4,4′-dimethoxybenzyl, benzyl, benzoin, benzophenone,2-benzoylbenzoic acid, 4,4′-bis(dimethylamino)benzophenone,4,4′-bis(diethylamino)benzophenone, benzoinmethyl ether, benzoinethylether, benzoinisopropyl ether, benzoinbutyl ether, benzoinisobutylether, 4-benzoylbenzoic acid,2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole,2-benzoylbenzoic acid methyl,2-(1,3-benzodioxole-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone,4,4′-dichlorobenzophenone, 2,2-diethoxyacetophenone,2,2-dimethoxy-2-phenylacetophenone, 2,4-diethylthioxanthen-9-one,diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO),1,4-dibenzoylbenzene, 2-ethylanthraquinone, 1-hydroxy cyclohexylphenylketone, 2-hydroxy-2-methylpropiophenone,2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone,2-isonitrosopropiophenone, and2-phenyl-2-(p-toluenesulfonyloxy)acetophenone.

The addition of a thermal decomposition radical generator can achievecuring. Illustrative example of the heat radical generator includes2,2′-azobis(isobutyronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylbutyronitrile), 4,4′-azobis(4-cyano laballenicacid), 2,2′-azobis(methylpropionamidine)hydrochloric acid,2,2′-azobis[2-(2-imidazoline-2-yl)propane]hydrochloric acid,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(cyclohexane-1-carbonitrile),1[(1-cyano-1-methylethyl)azo]formamide,2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis[N-(2-propenyl)-2-methylpropionamide],2,2′-azobis(N-butyl-2-methylpropionamide), dimethyl-2,2′-azobis(isobutyrate), 4,4′-azobis (4-cyano pentanoic acid),dimethyl-2,2′-azobis(2-methyl propionate), benzoyl peroxide,tert-butylhydro peroxide, cumenehydro peroxide, di-tert-butyl peroxide,di-tert-amyl peroxide, di-n-butyl peroxide,dimethyl-2,2′-azobis(2-methylpropronate), and dicumyl peroxide.

Illustrative example of the photo acid generator includes a sulfoniumsalt, an iodonium salt, sulfonyl diazomethane, N-sulfonyl oximide, andoxime-O-sulfonate acid generator. Illustrative example of the photo acidgenerator includes those disclosed in Japanese Unexamined Patentpublication (Kokai) No. 2008-111103 (paras. [0122] to [0142]) andJapanese Unexamined Patent publication (Kokai) No. 2009-080474.

The amount of the radical generator or the photo acid generator to beadded is preferably 0.1 to 50 parts by mass relative to 100 parts bymass of a resin.

Particularly, among these, the resin of the component (B) may preferablybe a silicone resin having a R_(x)SiO_((4-x)/2) unit, wherein Rrepresents a substituted or an unsubstituted monovalent hydrocarbongroup having 1 to 10 carbon atoms; and x represents a number of 2.5 to3.5, and a SiO₂ unit, diorganosiloxane having an alkenyl group, andorganohydrogen polysiloxane having a SiH group.

Tackiness Imparting Agent

Also, to provide adhesion to a living body for the bio-electrodecomposition of the present invention, a tackiness imparting agent may beadded. Illustrative example of the tackiness imparting agent includes asilicone resin, non-crosslinking siloxane, non-crosslinkingpoly(meth)acrylate, and non-crosslinking polyether.

Organic Solvent

Also, an organic solvent can be added to the bio-electrode compositionof the present invention. Illustrative example of the organic solventincludes an aromatic hydrocarbon solvent such as toluene, xylene,cumene, 1,2,3-trimethyl benzene, 1,2,4-trimethyl benzene,1,3,5-trimethyl benzene, styrene, cmethyl styrene, butyl benzene,sec-butyl benzene, isobutyl benzene, cymene, diethyl benzene,2-ethyl-p-xylene, 2-propyl toluene, 3-propyl toluene, 4-propyl toluene,1,2,3,5-tetramethyl toluene, 1,2,4,5-tetramethyl toluene, tetrahydronaphthalene, 4-phenyl-1-butene, tert-amyl benzene, amyl benzene,2-tert-butyl toluene, 3-tert-butyl toluene, 4-tert-butyl toluene,5-isopropyl-m-xylene, 3-methylethyl benzene, tert-butyl-3-ethyl benzene,4-tert-butyl-o-xylene, 5-tert-butyl-m-xylene, tert-butyl-p-xylene,1,2-diisopropyl benzene, 1,3-diisopropyl benzene, 1,4-diisopropylbenzene, dipropyl benzene, 3,9-dodecadiyne, pentamethyl benzene,hexamethyl benzene, hexyl benzene, 1,3,5-triethyl benzene; an aliphatichydrocarbon-based solvent such as n-heptane, isoheptane, 3-methylhexane, 2,3-dimethyl pentane, 3-ethyl pentane, 1,6-heptadiene,5-methyl-1-hexyne, norbornane, norbornene, dichloropentadiene,1-methyl-1,4-cyclohexadiene, 1-heptine, 2-heptine, cycloheptane,cycloheptene, 1,3-dimethyl cyclopentane, ethyl cyclopentane, methylcyclohexane, 1-methyl-1-cyclohexene, 3-methyl-1-cyclohexene, methylenecyclohexane, 4-methyl-1-cyclohexene, 2-methyl-1-hexene,2-methyl-2-hexene, 1-heptene, 2-heptene, 3-heptene, n-octane,2,2-dimethyl hexane, 2,3-dimethyl hexane, 2,4-dimethyl hexane,2,5-dimethyl hexane, 3,3-dimethyl hexane, 3,4-dimethyl hexane,3-ethyl-2-methyl pentane, 3-ethyl-3-methyl pentane, 2-methyl heptane,3-methyl heptane, 4-methyl heptane, 2,2,3-trimethyl pentane,2,2,4-trimethyl pentane, cyclooctane, cyclooctene, 1,2-dimethylcyclohexane, 1,3-dimethyl cyclohexane, 1,4-dimethyl cyclohexane, ethylcyclohexane, vinyl cyclohexane, isopropyl cyclopentane,2,2-dimethyl-3-hexene, 2,4-dimethyl-1-hexene, 2,5-dimethyl-1-hexene,2,5-dimethyl-2-hexene, 3,3-dimethyl-1-hexene, 3,4-dimethyl-1-hexene,4,4-dimethyl-1-hexene, 2-ethyl-1-hexene, 2-methyl-1-heptene, 1-octene,2-octene, 3-octene, 4-octene, 1,7-octadiene, 1-octyne, 2-octyne,3-octyne, 4-octyne, n-nonane, 2,3-dimethyl heptane, 2,4-dimethylheptane, 2,5-dimethyl heptane, 3,3-dimethyl heptane, 3,4-dimethylheptane, 3,5-dimethyl heptane, 4-ethyl heptane, 2-methyl octane,3-methyl octane, 4-methyl octane, 2,2,4,4-tetramethyl pentane,2,2,4-trimethyl hexane, 2,2,5-trimethyl hexane, 2,2-dimethyl-3-heptene,2,3-dimethyl-3-heptene, 2,4-dimethyl-1-heptene, 2,6-dimethyl-1-heptene,2,6-dimethyl-3-heptene, 3,5-dimethyl-3-heptene,2,4,4-trimethyl-1-hexene, 3,5,5-trimethyl-1-hexene, 1-ethyl-2-methylcyclohexane, 1-ethyl-3-methyl cyclohexane, 1-ethyl-4-methyl cyclohexane,propyl cyclohexane, isopropyl cyclohexane, 1,1,3-trimethyl cyclohexane,1,1,4-trimethyl cyclohexane, 1,2,3-trimethyl cyclohexane,1,2,4-trimethyl cyclohexane, 1,3,5-trimethyl cyclohexane, allylcyclohexane, hydrindane, 1,8-nonadiene, 1-nonyne, 2-nonyne, 3-nonyne,4-nonyne, 1-nonene, 2-nonene, 3-nonene, 4-nonene, n-decane, 3,3-dimethyloctane, 3,5-dimethyl octane, 4,4-dimethyl octane, 3-ethyl-3-methylheptane, 2-methyl nonane, 3-methyl nonane, 4-methyl nonane, tert-butylcyclohexane, butyl cyclohexane, isobutyl cyclohexane,4-isopropyl-1-methyl cyclohexane, pentyl cyclopentane,1,1,3,5-tetramethyl cyclohexane, cyclododecane, 1-decene, 2-decene,3-decene, 4-decene, 5-decene, 1,9-decadiene, decahydronaphthalene,1-decyne, 2-decyne, 3-decyne, 4-decyne, 5-decyne, 1,5,9-decatriene,2,6-dimethyl-2,4,6-octatriene, limonene, myrcene, 1,2,3,4,5-pentamethylcyclopentadiene, α-phellandrene, pinene, terpinene,tetrahydrodicyclopentadiene, 5,6-dihydrodicyclopentadiene,dichloropentadiene, 1,4-decadiyne, 1,5-decadiyne, 1,9-decadiyne,2,8-decadiyne, 4,6-decadiyne, n-undecane, amyl cyclohexane, 1-undecene,1,10-undecadiene, 1-undecyne, 3-undecyne, 5-undecyne,tricyclo[6.2.1.0^(2,7)]undeca-4-en, n-dodecane, 2-methyl undecane,3-methyl undecane, 4-methyl undecane, 5-methyl undecane,2,2,4,6,6-pentamethyl heptane, 1,3-dimethyladamantane,1-ethyladamantane, 1,5,9-cyclododecatriene, 1,2,4-trivinyl cyclohexane,isoparaffin; a ketone-based solvent such as cyclohexanone,cyclopentanone, 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone,4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, and methyln-pentyl ketone; an alcohol-based solvent suchas 3-methoxy butanol, 3-methyl-3-methoxy butanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; an ether-based solvent such as propylene glycolmonomethyl ether, ethylene glycol monomethyl ether, propylene glycolmonoethyl ether, ethylene glycol monoethyl ether, propylene glycoldimethyl ether, diethylene glycol dimethyl ether, diisopropyl ether,diisobutyl ether, diisopentyl ether, di-n-pentyl ether, methylcyclopentyl ether, methyl cyclohexyl ether, di-n-butyl ether,di-secbutyl ether, disec-pentyl ether, di-tert-amyl ether, di-n-hexylether, and anisole; an ester-based solvent such as propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxy propionate, tert-butyl acetate, tert-butylpropionate, propylene glycol monotert-butyl ether acetate; and alactone-based solvent such as γ-butyrolactone.

The amount of the organic solvent to be added is preferably 10 to 50,000parts by mass relative to 100 parts by mass of a polymer.

Carbon Material

A carbon material can be added to the bio-electrode composition of thepresent invention as a conductive improver to further enhance theconductivity. Illustrative example of the carbon material includescarbon black and carbon nanotube, and carbon fibers. The carbon nanotubemay be either single-layer or multi-layer, and the surface may bemodified with an organic group. The amount of the carbon material to beadded is preferably in the range of 1 to 50 parts by mass relative to100 parts by mass of a polymer.

Conductive improver other than carbon material A conductive improverother than a carbon material can be added to the bio-electrodecomposition of the present invention. Illustrative example thereofincludes a particle, a fiber and a nanowire for coating a resin with aprecious metal such as gold, silver, and platinum, a nanoparticle suchas gold, silver, and platinum, and a particle of metal oxide such asindium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, and zincoxide.

As described above, the bio-electrode composition of the presentinvention can form a living body contact layer that is capable ofefficiently converting changes in ion concentration from the skin intoelectric signals and efficiently transmitting such electric signals to adevice (or that is excellent in conductivity), generating no allergydespite its long-time attachment to the skin (or that is excellent inbiocompatibility), is light-weight, can be manufactured at low cost, andcan control significant reduction in conductivity even though thebio-electrode is soaked in water or dried. Also, the addition of acarbon material can further improve the conductivity, and a combined useof adhesive and elastic polymers can manufacture particularly adhesiveand elastic bio-electrodes. Furthermore, the use of additives canimprove the elasticity and adhesion to the skin. The resin constituentand the thickness of a living body contact layer can be adjusted asrequired to control the elasticity and adhesion.

Bio-Electrode

The present invention provides a bio-electrode including a conductivesubstrate and a living body contact layer formed on the conductivesubstrate, wherein the living body contact layer is a cured product ofthe bio-electrode composition of the present invention.

The bio-electrode of the present invention will be described in detailwith reference to the drawings, but the present invention is notrestricted thereto.

FIG. 1 is a schematic cross-sectional view showing one example of abio-electrode of the present invention. In FIG. 1, a bio-electrode 1includes a conductive substrate 2 and a living body contact layer 3formed on the conductive substrate 2. The living body contact layer 3 isa layer in which an ionic polymer (ionic material) 4 and a carbonmaterial 5 are dispersed in a resin 6.

When such a bio-electrode 1 illustrated in FIG. 1 is used, asillustrated in FIG. 2, a living body contact layer 3 (or, a layer inwhich an ionic polymer 4 and a carbon material 5 are dispersed in aresin 6) is brought in contact with a living body 7 to take electricsignals out of the living body 7 by the ionic polymer 4 and the carbonmaterial 5, and the electric signals are transmitted via the conductivesubstrate 2 to a sensor device (not shown). Accordingly, thebio-electrode of the present invention can satisfy both conductivity andbiocompatibility by the ionic polymer (ionic material). As required, aconductive improver such as carbon material can be added to furtherimprove the conductivity, and its adhesion can keep constant the contactarea with the skin and stably obtain electric signals from the skin withhigh sensitivity.

Each component of the bio-electrode of the present invention will bedescribed in more detail.

Conductive Substrate

The bio-electrode of the present invention includes a conductivesubstrate. The conductive substrate is normally electrically connectedto a sensor device unit to transmit electric signals taken out of aliving body via a living body contact layer to the sensor device unit.

The conductive substrate is not particularly restricted so long as it isconductive, but preferably includes one or more substances selected fromgold, silver, silver chloride, platinum, aluminum, magnesium, tin,tungsten, iron, copper, nickel, stainless, chromium, titanium, andcarbon.

The conductive substrate is not particularly restricted, but may be ahard conductive substrate, a flexible conductive film, a fabric coatedwith a conductive paste on the surface, or a fabric weaved with aconductive polymer. The conductive substrate may be selected accordingto use of a bio-electrode e.g., flat, irregular or mesh weaved withmetal wire.

Living Body Contact Layer

The bio-electrode of the present invention includes a living bodycontact layer formed on the conductive substrate. The living bodycontact layer is in contact with a living body when the bio-electrode isused, having conductivity and adhesion. The living body contact layer isa cured product of the bio-electrode composition of the presentinvention, or an adhesive resin layer including the (A) ionic material(salt) and the (B) resin, and as required, an additive such as carbonmaterial.

The adhesive strength of a living body contact layer is preferably0.5N/25 mm or more and 20N/25 mm or less. The method for measuring anadhesive strength is commonly stipulated according to JUS Z 0237standards. The substrate may be a metal substrate such as SUS (stainlesssteel) or a PET (polyethylene terephthalate) substrate, but human skincan be used for measurement. The human skin has lower surface energythan metals and plastics, and it is as low as Teflon (registeredtrademark), and the skin is less likely to adhere.

The thickness of the living body contact layer of the bio-electrode ispreferably 1 μm or more and 5 mm or less, and more preferably 2 μm ormore and 3 mm or less. A thinner living body contact layer demonstrateslower adhesive strength, but improved flexibility, and light-weight andthen favorable compatibility with the skin. The thickness of a livingbody contact layer can be selected in view of adhesion and touch feelingto the skin.

In the bio-electrode of the present invention, as in a conventionalbio-electrode (e.g., a bio-electrode disclosed in Japanese UnexaminedPatent publication (Kokai) No. 2004-033468), an additional adhesive filmmay be provided on a living body contact layer to prevent thebio-electrode from peeling from the living body when in use. In thiscase, an adhesive film may be formed of an acrylic, a urethane, or asilicone adhesive film material. In particular, a silicone adhesive filmmaterial has high oxygen permeability, allowing for dermal respirationwith the same attached to the skin. Its higher water repellency can alsocontrol reduction in adhesion by sweating, and the stimulation to theskin is advantageously low. In the bio-electrode of the presentinvention, as described above, the addition of a tackiness impartingagent to a bio-electrode composition or use of a resin favorablyadhesive to a living body can prevent peeling from the living body,thereby saving the above additional adhesive film.

When the bio-electrode of the present invention is used as a wearabledevice, wires for connecting a bio-electrode and a sensor device andother members are not particularly restricted, but those disclosed ine.g., Japanese Unexamined Patent publication (Kokai) No. 2004-033468 canbe employed.

As described above, the bio-electrode of the present invention can forma living body contact layer formed of a cured product of thebio-electrode composition of the present invention that is capable ofefficiently transmitting electric signals from the skin to a device (or,that is excellent in conductivity), generating no allergy despite itslong-time attachment to the skin (or, that is excellent inbiocompatibility), is light-weight, can be manufactured at low cost, andcan control significant reduction in conductivity even though thebio-electrode is soaked in water or dried. The addition of a carbonmaterial can further improve the conductivity, and a combination ofadhesive and elastic polymers can manufacture a particularly highlyadhesive, elastic bio-electrode. Furthermore, the use of additives canimprove the elasticity and adhesion to the skin. The resin constituentand the thickness of a living body contact layer can be adjusted asrequired to control the elasticity and adhesion. Accordingly, such abio-electrode of the present invention is particularly desirable as abio-electrode used in medical wearable devices.

A Method for Manufacturing a Bio-Electrode

The present invention provides a method for manufacturing abio-electrode including a conductive substrate and a living body contactlayer formed on the conductive substrate, including: applying thebio-electrode composition of the present invention to the conductivesubstrate to be cured to form the living body contact layer.

A conductive substrate, a bio-electrode composition and others used inthe method for manufacturing a bio-electrode of the present inventionmay represent the same meanings as before.

The method for applying a bio-electrode composition to a conductivesubstrate is not particularly restricted, but such methods as dippingcoat, spraying coat, spin coat, roll coat, flow coat, doctor coat,screen printing, flexographic printing, gravure printing, and ink-jetprinting are desirable.

The method for curing a resin is not particularly restricted and may beselected according to the type of (B) resin used in the bio-electrodecomposition, preferably e.g., by heating and/or light exposure. Also, acatalyst for generating an acid or a base can be added to thebio-electrode composition, thereby generating a crosslinking reaction tocure a resin.

The heating temperature is not particularly restricted and may beselected according to the type of (B) resin used in the bio-electrodecomposition, preferably e.g., 50 to 250° C.

The resin may be cured by heating and light exposure at the same time,or first light exposure and then heating, or vice versa. The resin maybe air-dried to evaporate a solvent prior to heating after filmapplication.

As described above, the method for manufacturing a bio-electrode of thepresent invention can readily manufacture the bio-electrode of thepresent invention that is excellent in conductivity andbiocompatibility, is light-weight, can be manufactured at low cost, andcan control significant reduction in conductivity even though thebio-electrode is soaked in water or dried.

EXAMPLE

The present invention will be described in detail with reference to theExamples and Comparative Examples, but the present invention is notrestricted thereto. “Me” refers to a methyl group, while “Vi” refers toa vinyl group.

Ionic polymers 1 to 13 blended into a bio-electrode composition solutionas an ionic material (conductive material) were synthesized as follows.A PGMEA solution including 30% by mass of each monomer was mixed in areaction vessel, and the reaction vessel was cooled down to −70° C. innitrogen atmosphere, subjected to reduced pressure for deaeration andnitrogen blow three times. After the product was heated at elevatedtemperatures up to room temperature, AIBN (azobisisobutyronitrile) wasadded by 0.01 mole relative to 1 mole of the total monomer as apolymerization initiator, heated at elevated temperatures up to 60° C.,and was reacted for 15 hours to obtain polymers. The constituent of thepolymers obtained was confirmed by ¹H-NMR after drying the solvent, andthe molecular weight (Mw) and the degree of dispersion (Mw/Mn) of thepolymers obtained were confirmed by gel permeation chromatography (GPC),using THF (tetrahydrofuran) as a solvent. The ionic polymers 1 to 13thus synthesized are shown as follows:

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

wherein, the repeating unit represents the average.

The structures of comparative salts 1 to 3 blended into bio-electrodecomposition solutions of Comparative Examples as ionic materials areshown as follows,

Siloxane compounds 1 to 4 blended into the bio-electrode compositionsolution as a silicone-based resin are shown as follows.

Siloxane Compound 1

Polydimethylsiloxane containing a vinyl group whose viscosity in a 30%toluene solution is 27,000 mPa·s, whose alkenyl group content is 0.007mole/100 g, and whose molecular chain terminal is encapsulated by aSiMe₂Vi group, was defined as a siloxane compound 1.

Siloxane Compound 2

Polysiloxane of an MQ resin composed of a Me₃SiO_(0.5) unit and a SiO₂unit (Me₃SiO_(0.5) unit/SiO₂ unit=0.8) in a 60% toluene solution wasdefined as a siloxane compound 2.

Siloxane Compound 3

40 parts by mass of vinyl group-containing polydimethylsiloxane whoseviscosity is 42,000 mPa·s in a 30% toluene solution, whose alkenyl groupcontent is 0.007 mole/100 g, and whose molecular chain terminal isencapsulated by an OH group, 100 parts by mass of polysiloxane of an MQresin composed of a Me₃SiO_(0.5) unit and a SiO₂ unit (Me₃SiO_(0.5)unit/SiO₂ unit=0.8) in a 60% toluene solution, and a solution composedof 26.7 parts by mass of toluene were subjected to dry distillation,heated for 4 hours and cooled, and the product was bonded topolydimethylsiloxane at the MQ resin to be defined as a siloxanecompound 3.

Siloxane Compound 4

KF-99 (Product from Shin-Etsu Chemical Co., Ltd.) was used asmethylhydrodiene silicone oil.

Also, a side chain polyether-modified KF-353 (Product from Shin-EtsuChemical Co., Ltd.) was used as polyether silicone oil composed of asilicone-based resin.

An acrylic polymer 1 blended into a bio-electrode composition solutionas an acrylic-based resin is shown as follows:

wherein, the repeating unit represents the average.

Silicone urethane acrylates 1 and 2 blended into a bio-electrodecomposition solution as a silicone-based, an acrylic-based, or aurethane-based resin are shown as follows,

wherein, the repeating unit represents the average.

Organic solvents blended into bio-electrode composition solutions areshown as follows.

PGMEA: propylene glycol-1-monomethyl ether-2-acetatePGME: propylene glycol-1-monomethyl ether

A radical generator, a platinum catalyst, and a conductive improver(carbon black, carbon nanotube, gold-coated particle, silver-coatedparticle, ITO particle) blended into bio-electrode composition solutionsas an additive are shown as follows.

Radical generator: V-601, Product from Wako Pure Chemical Industries,Ltd.Platinum catalyst: CAT-PL-50T, Product from Shin-Etsu Chemical Co., Ltd.Carbon black: Denka Black HS-100, Product from Denka Company Limited.Multi-layer carbon nanotube: Product from Sigma-Aldrich Co. LLC. 110 to170 nm in diameter, 5 to 9 μm in lengthGold-coated particle: Micropearl AU (100 μm in diameter), Product fromSEKISUI CHEMICAL CO., LTD.Silver-coated particle: silver-coated powder (30 μm in diameter),Product from MITSUBISHI MATERIALS CorporationITO particle: ITO powder (0.03 μm in diameter), Product from MITSUBISHIMATERIALS Corporation

Examples 1 to 17, Comparative Examples 1 to 5

Ionic materials (salts), resins, organic solvents, and additives(radical generator, platinum catalyst, and conductive improver) wereblended with the constituents described in Tables 1 and 2 to preparebio-electrode composition solutions (bio-electrode composition solutions1 to 17 and Comparative bio-electrode composition solutions 1 to 5).

TABLE 1 Bio-electrode composition Ionic material Resin Organic solventAdditive solution (parts by mass) (parts by mass) (parts by mass) (partsby mass) Bio-electrode Ionic polymer Siloxane compound 1 (40) Toluene(30) Platinum catalyst (1.5) composition 1 (20) Siloxane compound 2(100) Carbon black (10) solution 1 Siloxane compound 4 (3) Bio-electrodeIonic polymer Siloxane compound 3 (126) Heptane (30) Platinum catalyst(0.7) composition 2 (20) Siloxane compound 4 (3) PGMEA (14) Carbon black(10) solution 2 Bio-electrode Ionic polymer Siloxane compound 1 (40)Toluene (30) Platinum catalyst (0.7) composition 3 (22.5) Siloxanecompound 2 (100) PGMEA (14) Carbon black (10) solution 3 Siloxanecompound 4 (3) Bio-electrode Ionic polymer Siloxane compound 1 (40)Toluene (30) Platinum catalyst (0.7) composition 4 (20) Siloxanecompound 2 (100) PGMEA (14) Carbon black (10) solution 4 Siloxanecompound 4 (3) Bio-electrode Ionic polymer Siloxane compound 3 (126)Toluene (44) Platinum catalyst (1.0) composition 5 (20) Siloxanecompound 4 (3) Carbon black (10) solution 5 KF-353 (2.5) Bio-electrodeIonic polymer Siloxane compound 3 (126) Toluene (30) Platinum catalyst(2.0) composition 6 (20) Siloxane compound 4 (3) 2-heptanone (14) Carbonblack (10) solution 6 KF-353 (26) Bio-electrode Ionic polymer Siloxanecompound 3 (126) Toluene (30) Platinum catalyst (1.0) composition 7 (25)Siloxane compound 4 (3) PGME (14) Carbon black (10) solution 7Bio-electrode Ionic polymer Siloxane compound 3 (126) Toluene (30)Platinum catalyst (1.5) composition 8 (24) Siloxane compound 4 (3) PGME(14) Carbon black (10) solution 8 Bio-electrode Ionic polymer Siloxanecompound 3 (126) Toluene (30) Platinum catalyst (1.5) composition 8 (24)Siloxane compound 4 (3) PGME (14) Multi-layered solution 9 carbonnanotube (6) Bio-electrode Ionic polymer Acrylic polymer 1 (60) PGMEA(100) Radical generator (4) composition 1 (20) Silicone urethaneacrylate 1 (20) Silver-coated solution 10 particle (40) Bio-electrodeIonic polymer Acrylic polymer 1 (55) PGMEA (100) Radical generator (4)composition 1 (20) Silicone urethane acrylate 1 (25) Gold-coatedsolution 11 particle (40) Bio-electrode Ionic polymer Acrylic polymer 1(60) PGMEA (100) Radical generator (4) composition 1 (20) Siliconeurethane acrylate 2 (20) ITO particle (40) solution 12 Bio-electrodeIonic polymer Siloxane compound 1 (40) Toluene (30) Platinum catalyst(1.5) composition 9 (20) Siloxane compound 2 (100) Carbon black (10)solution 13 Siloxane compound 4 (3) Bio-electrode Ionic polymer Siloxanecompound 3 (126) Heptane (30) Platinum catalyst (1.7) composition 10(20) Siloxane compound 4 (3) PGMEA (14) Carbon black (10) solution 14Bio-electrode Ionic polymer Siloxane compound 1 (40) Toluene (30)Platinum catalyst (1.7) composition 11 (22.5) Siloxane compound 2 (100)PGMEA (14) Carbon black (10) solution 15 Siloxane compound 4 (3)Bio-electrode Ionic polymer Siloxane compound 1 (40) Toluene (30)Platinum catalyst (1.7) composition 12 (20) Siloxane compound 2 (100)PGMEA (14) Carbon black (10) solution 16 Siloxane compound 4 (3)Bio-electrode Ionic polymer Siloxane compound 1 (40) Toluene (30)Platinum catalyst (1.7) composition 13 (20) Siloxane compound 2 (100)PGMEA (14) Carbon black (10) solution 17 Siloxane compound 4 (3)

TABLE 2 Bio-electrode composition Ionic material Resin Organic solventAdditive solution (parts by mass) (parts by mass) (parts by mass) (partsby mass) Comparative Comparative Siloxane compound 3 (126) Toluene (30)Platinum catalyst (1.0) bio-electrode salt 1 (4.7) Siloxane compound 4(3) PGME (14) Carbon black (10) composition solution 1 ComparativeComparative Siloxane compound 3 (126) Toluene (30) Platinum catalyst(1.0) bio-electrode salt 2 (8.2) Siloxane compound 4 (3) PGME (14)Carbon black (10) composition solution 2 Comparative ComparativeSiloxane compound 3 (126) Toluene (30) Platinum catalyst (1.0)bio-electrode salt 3 (8.4) Siloxane compound 4 (3) PGME (14) Carbonblack (10) composition solution 3 Comparative — Siloxane compound 3(126) Toluene (30) Platinum catalyst (1.0) bio-electrode Siloxanecompound 4 (3) PGME (14) Carbon black (10) composition solution 4Comparative Ionic polymer — PGMEA (100) Carbon black (10) bio-electrode1 (100) composition solution 5

Evaluation of Conductivity

A bio-electrode composition solution was applied to an aluminum disk 3cm in diameter and 0.2 mm in thickness using an applicator, air-dried atroom temperature for 6 hours, and then baked in nitrogen atmosphere at120° C. for 30 minutes using an oven to be cured to prepare 4bio-electrodes per one bio-electrode composition solution. Each of thebio-electrodes thus obtained, as illustrated in FIGS. 3(a) and 3(b),includes a living body contact layer 3 on one surface, and an aluminumdisk 8 as a conductive substrate on the other surface. Then, asillustrated in FIG. 3 (b), a copper wire 9 is attached to the surface ofthe aluminum disk 8 on a side that is not covered with the living bodycontact layer with adhesive tape, which was defined as an extractionelectrode, and this electrode was connected to an impedance voltagetransducer. As illustrated in FIG. 4, 2 bio-electrodes 1′ were appliedto the arm's skin so that the skin was connected to the living bodycontact layer side, with an interval of 15 cm. The initial impedance wasmeasured with an alternating current impedance voltage transducer SI1260 from Solartron Corporation with various frequencies. Then, afterthe two residual bio-electrodes were immersed in pure water for one hourand the water was dried, the impedance on the skin was measured by theabove method. Table 3 shows the impedance with a frequency of 1,000 Hz.

Evaluation of Adhesion

Each of the bio-electrode composition solutions was applied to a PEN(polyethylene naphthalate) substrate 100 μm in thickness using anapplicator, and air-dried at room temperature for 6 hours, then using anoven, baked in nitrogen atmosphere at 120° C. for 30 minutes to be curedto prepare an adhesive film. A 25 mm-width tape was cut from theadhesive film, and this was attached to a stainless plate (SUS304) bypressure, and left unattended at room temperature for 20 hours. Theforce for requiring a tape prepared from the adhesive film to peel fromthe stainless plate at a speed of 300 mm/min with an angle of 180degrees (N/25 mm) was measured with a tensile tester. Table 3 shows theresults.

Measurement of Thickness of Living Body Contact Layer

In the bio-electrodes prepared in the conductivity evaluation test, thethickness of living body contact layers was measured with a micrometer.Table 3 shows the results.

TABLE 3 Bio-electrode adhesion Thickness of Initial Impedance afterwater composition solution (N/25mm) resin (μm) impedance(Ω) immersion(Ω)Example 1 Bio-electrode 3.2 610 2.8E⁴ 2.3E⁴ composition solution 1Example 2 Bio-electrode 3.2 460 1.8E⁴ 1.1E⁴ composition solution 2Example 3 Bio-electrode 3.5 510 7.2E³ 9.3E³ composition solution 3Example 4 Bio-electrode 2.1 480 4.8E⁴ 5.1E⁴ composition solution 4Example 5 Bio-electrode 2.4 490 8.2E⁴ 8.9E⁴ composition solution 5Example 6 Bio-electrode 4.2 560 4.0E³ 4.3E³ composition solution 6Example 7 Bio-electrode 2.2 580 6.9E³ 6.0E³ composition solution 7Example 8 Bio-electrode 1.9 430 7.0E⁴ 7.8E⁴ composition solution 8Example 9 Bio-electrode 2.1 520 3.2E⁴ 3.9E⁴ composition solution 9Example 10 Bio-electrode 2.8 650 6.2E⁴ 6.3E⁴ composition solution 10Example 11 Bio-electrode 3.1 690 8.4E⁴ 8.8E⁴ composition solution 11Example 12 Bio-electrode 3.1 670 9.9E⁴ 9.6E⁴ composition solution 12Example 13 Bio-electrode 2.2 570 5.6E³ 5.5E³ composition solution 13Example 14 Bio-electrode 2.6 550 5.2E³ 6.0E³ composition solution 14Example 15 Bio-electrode 2.9 500 3.2E³ 3.0E³ composition solution 15Example 16 Bio-electrode 2.3 520 2.8E³ 2.2E³ composition solution 16Example 17 Bio-electrode 2.4 550 2.4E³ 2.5E³ constituent solution 17Comparative Comparative bio-electrode 2.3 520 4.2E⁴ 5.3E⁵ Example 1composition solution 1 Comparative Comparative bio-electrode 2.2 5305.2E⁴ 7.3E⁵ Example 2 composition solution 2 Comparative Comparativebio-electrode 2.6 520 5.1E⁴ 8.3E⁵ Example 3 composition solution 3Comparative Comparative bio-electrode 4.5 540 9.9E⁶ 9.9E⁶ Example 4composition solution 4 Comparative Comparative bio-electrode 0 430 4.9E⁵4.8E⁵ Example 5 composition solution 5

As illustrated in Table 3, Examples 1 to 17 showed the living bodycontact layers formed of the bio-electrode compositions of the presentinvention including a salt having a specific structure (ionic material)and a resin. The initial impedance was low, and even after thebio-electrode was immersed in water and dried, no significant change inimpedance was found. In the bio-electrodes obtained in Examples 1 to 17,the initial conductivity was high, and there were no significantreductions in conductivity even though the bio-electrode was soaked inwater or dried. These bio-electrodes in Examples 1 to 17 demonstrateadhesion as favorable as those in Comparative Examples 1 to 3 whereconventional salts and resins were blended, are light-weight, excellentin biocompatibility, and can be manufactured at low cost.

Meanwhile, Comparative Examples 1 to 3 showed the living body contactlayers formed of the bio-electrode compositions including conventionalsalts and resins. Although the initial impedance was low, the impedancesignificantly increased to a higher-digit number after the bio-electrodewas immersed in water and dried. The bio-electrodes in ComparativeExamples 1 to 3 demonstrated a high initial conductivity, but when theywere soaked in water or dried, all the conductivity values significantlydeclined.

Comparative Example 4 showed the living body contact layer formed of thebio-electrode composition including a resin, instead of a salt. Non-saltcontent caused no significant higher-digit increase in impedance evenafter the bio-electrode was immersed in water and dried, but the initialimpedance was high. All the bio-electrodes in Comparative Example 4showed low initial conductivity.

Comparative Example 5 showed the living body contact layer formed of thebio-electrode composition including a salt, instead of a resin. Thecontent of salt, as in the Example, caused no significant higher-digitincrease in impedance even after the bio-electrode was immersed in waterand dried, but non-adhesive resin content caused no high adhesivestrength, thereby generating high impedance (initial impedance) to theskin. Specifically, all the bio-electrodes in Comparative Example 5showed low initial conductivity.

The above observations found that the bio-electrode for forming a livingbody contact layer, using the bio-electrode composition of the presentinvention, is excellent in conductivity, biocompatibility, adhesion to aconductive substrate, and holding force of an ionic material. Such abio-electrode doesn't significantly decline the conductivity even thoughthe bio-electrode is soaked in water or dried, is light-weight, and canbe manufactured at low cost.

While this invention has been described with an emphasis upon preferredembodiments, it will be obvious to those of ordinary skill in the artthat variations of the preferred embodiments may be used and that it isintended that the invention may be practiced otherwise than asspecifically described herein.

Accordingly, this invention includes all modifications encompassedwithin the spirit and scope of the invention as defined by the followingclaims.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   1, 1′ . . . Bio-electrode, 2 . . . Conductive substrate, 3 . . .        Living body contact layer,    -   4 . . . Ionic polymer (ionic material), 5 . . . Carbon material,        6 . . . Resin, 7 . . . Living body, 8 . . . Aluminum disk, 9 . .        . Copper wire.

What is claimed is:
 1. A bio-electrode comprising a conductive substrateand a living body contact layer formed on the conductive substrate,wherein the living body contact layer is a cured product of abio-electrode composition, the bio-electrode composition comprising an(A) ionic material and a (B) resin other than the ionic material (A),wherein the ionic material (A) comprises both a repeating unit “a” of alithium salt, a sodium salt, a potassium salt, or an ammonium salt ofsulfonamide comprising a partial structure represented by the followinggeneral formula (1) and a repeating unit “b” comprising a silicon atom,the general formula (1) being:—R¹—C(═O)—N⁻—SO₂—Rf₁M⁺  (1) wherein, R¹ represents a single bond, or alinear, a branched, or a cyclic divalent hydrocarbon group comprising 1to 40 carbon atoms, which may be substituted by a heteroatom, ormediated by a heteroatom; Rf₁ represents a linear or a branched alkylgroup comprising 1 to 4 carbon atoms or a phenyl group, comprising oneor more fluorine atoms or a trifluoromethyl group; and M⁺ represents anyof a lithium ion, a sodium ion, a potassium ion, or an ammonium ion. 2.The bio-electrode according to claim 1, wherein the conductive substratecomprises one or more substances selected from gold, silver, silverchloride, platinum, aluminum, magnesium, tin, tungsten, iron, copper,nickel, stainless, chromium, titanium, and carbon.
 3. A method formanufacturing a bio-electrode comprising a conductive substrate and aliving body contact layer formed on the conductive substrate,comprising: applying a bio-electrode composition to the conductivesubstrate to be cured to form the living body contact layer; wherein thebio-electrode composition comprises an (A) ionic material and a (B)resin other than the ionic material (A), wherein the ionic material (A)comprises both a repeating unit “a” of a lithium salt, a sodium salt, apotassium salt, or an ammonium salt of sulfonamide comprising a partialstructure represented by the following general formula (1) and arepeating unit “b” comprising a silicon atom, the general formula (1)being:—R¹—C(═O)—N⁻—SO₂—Rf₁M⁺  (1) wherein, R¹ represents a single bond, or alinear, a branched, or a cyclic divalent hydrocarbon group comprising 1to 40 carbon atoms, which may be substituted by a heteroatom, ormediated by a heteroatom; Rf₁ represents a linear or a branched alkylgroup comprising 1 to 4 carbon atoms or a phenyl group, comprising oneor more fluorine atoms or a trifluoromethyl group; and M⁺ represents anyof a lithium ion, a sodium ion, a potassium ion, or an ammonium ion. 4.The method for manufacturing a bio-electrode according to claim 3,wherein the conductive substrate comprises one or more substancesselected from gold, silver, silver chloride, platinum, aluminum,magnesium, tin, tungsten, iron, copper, nickel, stainless, chromium,titanium, and carbon.